ARLINGTON, Texas — Eventually the Yankees will have to set their starting rotation for the ALDS that starts Oct. 4 at Yankee Stadium.

With James Paxton, Luis Severino and Masahiro Tanaka set to face the Rangers in the final three games of the regular season, it’s not hard to guess how the Yankees will go for the first three postseason games.

Based on using starters CC Sabathia and J.A. Happ out of the bullpen against the Rays on Tuesday and Wednesday nights, respectively, the Yankees could use Chad Green as an opener in Game 4 of the best-of-five affair if the gas-throwing right-hander isn’t needed in the second or third game. That would give the AL East champions two veteran lefties in the pen.

Nevertheless, the 36-year-old Happ’s resurgence in the last six games (five starts) might give the Yankees the thought to use him as a starter, which would free Green to be used later in the game.

“I don’t think anything is set in stone,’’ Happ said after allowing a run and four hits and striking out six in five innings of Wednesday night’s 4-0 loss to the Rays after Jonathan Loaisiga worked the first inning when Green wasn’t available. “Anything I can do to help us win.’’

The Yankees have won four of those five starts and Happ is 2-0 with a 2.23 ERA and has held hitters to a .177 batting average. In 32 ¹/₃ innings, Happ has allowed 20 hits, fanned 35 and walked 12.

“Continuing to build on what has been a good stretch for him,’’ Aaron Boone said of Happ, who is 12-8 with a 4.91 ERA in 31 games (30 starts).

With Green in a Dellin Betances-type stretch, it might make more sense to save him for later in the game than to open with him. In Green’s last 10 appearances, he has allowed four hits and struck out 32 in 16 ²/₃ innings and held hitters to a .296 OPS.